Bumper system for motor vehicles

ABSTRACT

A bumper system for a motor vehicle includes an energy absorber and a bumper beam interconnecting the energy absorber and vehicle structure. The bumper system also includes a push bar disposed below and operatively connected to the bumper beam to deflect and rotate during an impact with an object by the bumper system.

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] The present application claims the priority date of co-pendingUnited States Provisional Patent Application Ser. No. 60/170,935, filedDec. 15,1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to bumpers for motorvehicles and, more specifically, to a bumper system for a motor vehicle.

[0004] 2. Description of the Related Art

[0005] It is known to provide a bumper system for a front end or rearend of a motor vehicle. For a front end of the motor vehicle, the bumpersystem typically includes a bumper beam extending transversely andsecured to a forward end of a pair of front rails, which extendlongitudinally and are spaced transversely. The bumper system alsoincludes an energy absorber extending transversely and in front of thebumper beam. The bumper system may include a fascia disposed over andcovering the energy absorber.

[0006] It is also known that the bumper system protects a body of themotor vehicle from low speed impact with an object through elastic orsemi-plastic deformation of the energy absorber. It is further knownthat the bumper system is an absorber for high-speed impact with anobject through major plastic deformation of the bumper beam.

[0007] It is further known that a bumper system may have a mechanicaldevice which either lowers down or pushes forward during certain vehicletravel speed to contain the low push bar design within the vehicleapproach angle requirement.

[0008] It is desirable to provide a bumper system with a lower leg pushbar that uses rotation of the push bar instead of its longitudinaldeformation to reduce the under side intrusion of lower leg into thevehicle. It is also desirable to prevent a pedestrian's lower leg frombeing over-ridden by the bumper during an impact. It is furtherdesirable to provide a bumper system with a pedestrian friendly deviceon a motor vehicle attached to a bumper beam made of spring steel thatstores and resists impact energies. Therefore, there is a need in theart to provide a bumper system for a motor vehicle that meets thesedesires.

SUMMARY OF THE INVENTION

[0009] Accordingly, the present invention is a bumper system for a motorvehicle. The bumper system includes an energy absorber and a bumper beaminterconnecting the energy absorber and vehicle structure. The bumpersystem also includes a push bar disposed below and operatively connectedto the bumper beam to deflect and rotate during an impact with an objectby the bumper system.

[0010] One advantage of the present invention is that a new bumpersystem is provided for a motor vehicle. Another advantage of the presentinvention is that the bumper system includes a lower leg push bar toprevent a pedestrian's leg from being over-ridden by the bumper duringan impact. Yet another advantage of the present invention is that thebumper system has a lower leg push bar that rotates downward in theoccurrence of vehicle impact with a leg of a pedestrian. Still anotheradvantage of the present invention is that the bumper system has a lowerleg push bar that is capable of rotating up and down in the case of curbor speed bump contact. A further advantage of the present invention isthat the bumper assembly includes a pedestrian friendly device attachedto a bumper beam made of spring steel that stores internal energiesrather than resist energies which may damage a pedestrian's leg duringincidental vehicle impact.

[0011] Other features and advantages of the present invention will bereadily appreciated, as the same becomes better understood, afterreading the subsequent description when considered in connection withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a perspective view of a bumper system, according to thepresent invention, illustrated in operational relationship with a motorvehicle.

[0013]FIG. 2 is a partial perspective view of the bumper system of FIG.1.

[0014]FIG. 3 is a fragmentary bottom view of the bumper system of FIG.1.

[0015]FIG. 4 is a fragmentary side elevational view of the bumper systemof FIG. 1.

[0016]FIG. 5 is a side elevational view of the bumper system of FIG. 1with a fascia removed.

[0017]FIG. 6 is a fragmentary elevational view of the bumper system ofFIG. 1 illustrating a first stage of a low-speed curb impact.

[0018]FIG. 7 is a view similar to FIG. 6 illustrating a second stage ofa low-speed curb impact.

[0019]FIG. 8 is a view similar to FIG. 6 illustrating a first stage of ahigh-speed pedestrian impact.

[0020]FIG. 9 is a view similar to FIG. 6 illustrating a second stage ofa high-speed pedestrian impact.

[0021]FIG. 10 is a fragmentary elevational view of another embodiment,according to the present invention, of the bumper system of FIG. 1.

[0022]FIG. 11 is a perspective view of a portion of the bumper system ofFIG. 10.

[0023]FIG. 12 is a perspective view of a portion of the bumper system ofFIG. 10.

[0024]FIG. 13 is a side elevational view of a portion of the bumpersystem of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0025] Referring to the drawings and in particular FIG. 1, oneembodiment of a bumper system 10, according to the present invention, isillustrated in operational relationship with a motor vehicle 12. Thebumper system 10 is disposed at a front or forward end of the motorvehicle 12. It should be appreciated that the bumper system 10 may bedisposed at a rear or rearward end of the motor vehicle 12. It shouldalso be appreciated that, except for the bumper system 10, the motorvehicle 12 is conventional and known in the art.

[0026] As illustrated in FIGS. 2 through 5, the bumper system 10includes a bumper beam, generally indicated at 16. The bumper beam 16extends laterally and is secured to a forward end 17 of a pair of frontrails 18 by suitable means such as welding or mechanical fastening. Itshould be appreciated that the bumper beam 16 may have any suitablecross-sectional shape.

[0027] In the embodiment illustrated, the bumper beam 16 is a hollowmember having a general “B” cross-sectional shape. The bumper beam 16has a front or impact wall 20 extending generally vertically andlaterally. The bumper beam 16 also has an upper or top wall 22 and alower or bottom wall 24 inclined from the impact wall 20 and extendinglaterally. The bumper beam 16 has a curved or arcuate forward cornerwall 26 interconnecting the impact wall 20 and the upper and lower walls22 and 24. The bumper beam 16 also has a rear or supporting wall 28extending generally vertically and laterally from the upper and lowerwalls 22 and 24. The bumper beam 16 has a curved or arcuate rear cornerwall 30 interconnecting the supporting wall 28 and the upper and lowerwalls 22 and 24. It should be appreciated that the impact wall 20 has aheight greater than the supporting wall 28.

[0028] The bumper beam 16 also has a plurality of, preferably twogenerally horizontal interior walls 32 extending laterally andlongitudinally forward toward the impact wall 20. The bumper beam 16 hasa curved or arcuate inner corner wall 34 interconnecting the interiorwalls 32 and supporting wall 28. The bumper beam 16 has an inclinedtransition wall 36 extending laterally and longitudinally forward fromthe interior walls 32 and toward a center of the impact wall 20 and acurved or arcuate projection wall 38 interconnecting the ends of thetransition walls 36. The impact wall 20 may be formed as two portionswith each portion extending from the front corner walls 26 and spacedvertically from each other to form a gap (not shown) therebetween. Theprojection wall 38 is secured to the upper and lower portions of theimpact wall 20 by suitable means such as welding or mechanical fasteningto increase a stability of the bumper beam 16 against a “match boxing”behavior. The upper and lower portions of the impact wall 20 may have aplurality of apertures (not shown) extending therethrough and spacedlaterally for a function to be described.

[0029] As illustrated in FIG. 5, a top wall of the rail 18 is locatedbetween the upper wall 22 and the top interior wall 32 of the bumperbeam 16 and a lower wall of the rail 18 is located between the lowerwall 24 and the lower interior wall 32 of the bumper beam 16 in asymmetrical manner. As a result, the stiffness of the rail 18 causes thetwo interior walls 32 to collapse prior to the upper and lower walls 22and 24 collapse. It should be appreciated that this overlapping collapseassures a uniform energy absorption characteristic in high-speedimpacts. It should also be appreciated that the walls 22, 24, and 32 mayhave a plurality of apertures (not shown) extending therethrough toachieve a desired crush stiffness of the bumper beam 16.

[0030] The bumper beam 16 is made of a relatively rigid material such asmetal. The bumper beam 16 is integral, unitary, and formed as one-pieceby manufacturing processes such as roll forming which a conventionalprocess known in the art. It should also be appreciated that othermanufacturing processes such as extruding and stamping may be used toform the bumper beam 16. It should also be appreciated that the bumperbeam 16 may be attached to a rearward end (not shown) of a pair of rearrails (not shown) of the motor vehicle 12 by suitable means such aswelding.

[0031] The bumper system 10 includes an energy absorber 44. The energyabsorber 44 extends laterally and is secured to the bumper beam 16. Theenergy absorber 44 may have a plurality of projections (not shown)extending rearward therefrom and through the apertures in the impactwall 20. The energy absorber 44 is a solid member having a generallytrapezoidal shape with rear upper and lower lips 48 and 50 extendingrearward. The upper and lower lips 48 and 50 have a generally arcuate orcurved shape to extend over the front corner walls 26 of the bumper beam16. The energy absorber 44 is made of a relatively deformable materialsuch as foam. The bumper beam 16 may have a horizontal sweep to reducethe depth of the deformable material of the energy absorber 44. Itshould be appreciated that the apertures in the impact wall 20 allowsthe energy absorber 44 to have local penetration in order to avoidexcess compacting of the deformable material during a high-speed impactwith an object (not shown).

[0032] Referring to FIGS. 1 and 4, the bumper system 10 further includesa fascia 50 extending laterally and vertically to cover the energyabsorber 44. The fascia 50 is secured to vehicle structure (not shown)by suitable means such as fasteners (not shown). The fascia 50 is madeof a relatively rigid material such as plastic. It should be appreciatedthat the fascia 50 is conventional and known in the art.

[0033] Referring to FIGS. 2 through 5, the bumper system 10 includes apedestrian lower leg push bar, generally indicated at 52, to limit amaximum lateral bending angle of a knee of a pedestrian 70 (FIGS. 7 and8) who contacts the vehicle 12. As illustrated, the lower leg push bar52 includes a push bar member 54 extending laterally across a front endof the vehicle 12 below or under the bumper beam 16 and energy absorber44. The push bar member 54 is generally planar and rectangular in shape.The push bar member 54 may have an arcuate or generally “U” shapedportion 56 at a forward end thereof to contact the pedestrian. The pushbar member 54 also includes at least one, preferably a plurality ofattachment portions 58 extending at a rear end thereof and spacedlaterally for attachment to either the bumper beam 16 or rails 18 in amanner to be described. The push bar member 54 is made of a relativelyrigid material such as a composite or metal material. The push barmember 54 is a monolithic structure being integral, unitary, andone-piece. It should be appreciated that the push bar member 54 has apre-designed horizontal downward angle.

[0034] The lower leg push bar 52 includes at least one, preferably aplurality of mechanical attachment devices 60 to attach the push barmember 54 to vehicle structure such as a lower face of the bumper beam16 or the rails 18. The mechanical attachment devices 60 include ahousing 62 attached to either the bumper beam 16 or rails 18 by suitablemeans such as welding. The mechanical attachment devices 60 also includea pin 64 extending through the attachment portions 58 of the push barmember 54 and the housing 62 to allow the push bar member 54 to rotaterelative to the bumper beam 16 or rails 18. It should be appreciatedthat the mechanical attachment devices 60 are conventional and known inthe art.

[0035] The lower leg push bar 52 includes at least one, preferably aplurality of springs 66 to urge the push bar member 54 toward a forwardposition and to control the stiffness of the lower leg push bar 52. Thesprings 66 are of a rotational type. One of the springs 66 is disposedin each of the housings 62 to cooperate with the pin 64. It should beappreciated that the springs 66 are conventional and known in the art.

[0036] In operation, the bumper system 10 has a first stage or mode asillustrated in FIGS. 6 and 7. In the first mode at low speeds (i.e.,less than or equal to approximately ten miles per hour), the bumpersystem 10 impacts an object such as a pothole or curb 68. In this case,the lower leg push bar 52 contacts the curb 68 and the impact forcerotates the lower leg push bar 52 backward or counter-clockwise to yieldto the incoming object. It should be appreciated that during a backup ofthe vehicle 12 from a steep driveway onto a relatively flat roadsurface, the front end of the vehicle 12 will have a mild “dive down”motion and the lower leg push bar 52 will be allowed to have clockwiserotation to avoid damage during this impact condition.

[0037] Referring to FIGS. 8 and 9, the bumper system 10 has a secondstage or mode as illustrated. In the second mode at high speeds (i.e.,greater than approximately ten miles per hour), the bumper system 10impacts an object such as a pedestrian 70. When a lower leg 72 of thepedestrian 70 contacts the lower leg push bar 52, this impact causes thepush bar member 54 to deform and initiates a downward counter-clockwisemovement. The force required to rotate the base member 54 will becontrolled by the stiffness of the springs 66 located in the mechanicalattachment devices 60. The deformation and the rotation of the push barmember 54 will absorb most of the impact energy on the lower leg 72. Aknee joint of the pedestrian 70 will compress the energy absorber 44 tominimize the acceleration of the knee joint. The energy absorber 44 willcover the knee height in order to minimize the shear deformation of theknee joint. An upper leg 74 of the pedestrian 70 will impact the top ofthe bumper through either the fascia 50 or grille 76. The deformation ofeither the fascia 50 or grille 76 will minimize intrusion of the upperleg 74 to the exterior surface of the vehicle 12. After the leg has beenaccelerated to the vehicle's speed, the springs 66 will rotate the pushbar member 54 back to its pre-impact position. It should be appreciatedthat the knee joint angle will be limited throughout the impact by theintrusion of the knee into the energy absorbing member 44, the lower leg72 intrusion under the bumper beam 16 controlled by the push bar member54, and the intrusion of the upper leg 74 into the 5 fascia 50 or grill76.

[0038] Referring to FIGS. 10 through 13, another embodiment 110,according to the present invention, of the bumper system 10 is shown.Like parts of the bumper system 10 have like reference numeralsincreased by one hundred (100). In this embodiment, the bumper system110 includes a spring device, generally indicated at 180, attaching thelower leg push bar 152 to the bumper beam 116. The spring device 180 hasa base wall 182 and side walls 184 extending generally perpendicularfrom the base wall 182 to form an inverted “U” shaped cross-section witha notch 185. The spring device 180 also has a reaction flange 186extending generally perpendicular to the base wall 184. The springdevice 180 includes at least one preferably a pair of apertures 188extending through the base wall 182 to receive fasteners 190 forattaching the spring device 180 to the lower leg push bar 152 and bumperbeam 116. The spring device 180 is made of a metal material such asspring steel, preferably a high strength steel that is above 50 ksi. Thespring device 180 is made by a stamping process in which the side walls184 have cuts for the notch 185 stamped therein and the spring device180 is folded into shape with the flanges of the cuts mechanicallyjoined by spot welding or fasteners (not shown) to form the notch 185.It should be appreciated that the adjoined flanges will bulk out ofplane in order to be compatible with the deflection and to achieve aconstant spring rate throughout the yielding of the flanges.

[0039] In operation, upon impact with a lower leg of a pedestrian, thepush bar member 154 of the lower leg push bar 152 begins to rotate andapplies a reaction force to the lower leg of the pedestrian. During thisbuild up of forces, the spring device 180 reacts with a controlledresistive force storing energy applied by the leg of the pedestrian. Thespring device 180 then applies a rebound force to the push bar member154 and leg controlling the angularity of the pedestrian leg at the kneejoint below a predetermined level. It should be appreciated that thespring device 180 allows the lower point of the push bar member 154 tobe positioned farther aft in the vehicle 12 than a non-spring supportedpush bar member 154, which is beneficial to vehicle packaging andstyling flexibility during new vehicle definition.

[0040] Accordingly, the spring device 180 provides attachment and jointstrength for fastening a lower leg push bar 152 to a bumper beam 116 orother armature positioned at the front of the vehicle 12. The springdevice 180 also provides strength and reaction forces to the push barmember 154 to resist breakage during incidental contact with any objectin the external environment such as curbs, driveways, etc. The springdevice 180 is tunable by changing its geometry length, width, materialthickness, and shape and is a simple structure to manufacture. Thespring device 180 provides elastic reaction and storage of internalenergies during an impact with a lower leg of a pedestrian, whichlengthens the time of contact between the push bar 162 and the lower legof the pedestrian, in turn, lowering the peak forces applied to the leg.The spring device 180 uses a high strength spring steel to “store”energy temporarily during the impact event instead of relying onpermanent material deformation to dissipate energy.

[0041] The present invention has been described in an illustrativemanner. It is to be understood that the terminology, which has beenused, is intended to be in the nature of words of description ratherthan of limitation.

[0042] Many modifications and variations of the present invention arepossible in light of the above teachings. Therefore, within the scope ofthe appended claims, the present invention may be practiced other thanas specifically described.

What is claimed is:
 1. A bumper system for a motor vehicle comprising:an energy absorber; a bumper beam connected to said energy absorber andfor connection to vehicle structure; and a push bar disposed below andoperatively connected to said bumper beam to deflect and rotate duringan impact with an object by said bumper system.
 2. A bumper system asset forth in claim 1 wherein said bumper beam is made of a metalmaterial.
 3. A bumper system as set forth in claim 1 wherein said pushbar has a push bar member extending laterally.
 4. A bumper system as setforth in claim 3 wherein said push bar member includes at least oneattachment portion extending outwardly therefrom.
 5. A bumper system asset forth in claim 4 wherein said push bar includes at least oneattachment device interconnecting said at least one attachment portionand either one of said bumper beam and the vehicle structure.
 6. Abumper system as set forth in claim 5 wherein said at least oneattachment device includes a housing attached to said bumper beam andthe vehicle structure and a pin extending through said at least oneattachment portion and said housing to allow said push bar member torotate.
 7. A bumper system as set forth in claim 3 including at leastone spring to urge said push bar member forward.
 8. A bumper system asset forth in claim 1 including a spring device connected to said pushbar and either one of said bumper beam and the vehicle structure.
 9. Abumper system as set forth in claim 8 wherein said spring device has abase wall and side walls extending perpendicularly from said base wallto form a “U” shaped cross section with notches in said side walls. 10.A bumper system as set forth in claim 9 wherein said base wall has aplurality of apertures extending therethrough.
 11. A bumper system asset forth in claim 10 including a plurality of fasteners extendingthrough said apertures, one of said fasteners connecting said springdevice to said push bar and one of said fasteners connecting said springdevice to either one said bumper beam and the vehicle structure.
 12. Abumper system as set forth in claim 8 wherein said spring device is madeof a high strength spring steel.
 13. A bumper system as set forth inclaim 1 wherein said push bar is made of either one of a metal materialand a composite material.
 14. A bumper system as set forth in claim 1wherein said energy absorber is made of a deformable material.
 15. Abumper system for a motor vehicle comprising: an energy absorber; abumper beam interconnecting said energy absorber and vehicle structure;and a push bar disposed below and operatively connected to said bumperbeam to deflect and rotate during an impact with an object by saidbumper system; and said push bar comprising a push bar member made of arelatively rigid material extending laterally across a front of themotor vehicle.
 16. A bumper system as set forth in claim 15 including aspring device connected to said push bar and either one of said bumperbeam and the vehicle structure.
 17. A bumper system as set forth inclaim 16 wherein said spring device is made of a high strength springsteel.
 18. A bumper system as set forth in claim 15 wherein said pushbar includes at least one attachment portion extending outwardlytherefrom from said push bar member.
 19. A bumper system as set forth inclaim 18 wherein said push bar includes at least one attachment deviceinterconnecting said at least one attachment portion and either one ofsaid bumper beam and the vehicle structure.
 20. A bumper system for amotor vehicle comprising: an energy absorber; a bumper beaminterconnecting said energy absorber and vehicle structure; and a pushbar disposed below and operatively connected to said bumper beam todeflect and rotate during an impact with an object by said bumpersystem; and a spring device connected to said push bar and either one ofsaid bumper beam and the vehicle structure.